Tanker cargo operations involve hazardous cargo environments, complex technical systems and stringent operational procedures. These conditions make accident analysis particularly demanding and require analytical approaches that consider the specific operational context of tanker cargo handling. Existing Human Factors Analysis and Classification System (HFACS) adaptations used in maritime safety research provide a useful framework for analysing human and organisational factors, but they do not fully capture the operational characteristics of tanker cargo operations. As a result, some factors specific to tanker cargo handling remain insufficiently represented in existing HFACS-based analyses. Therefore, this study develops and validates a domain-specific HFACS framework for tanker cargo operations (HFACS-TCO) and applies it to the analysis of accident investigation reports. The framework was developed through an iterative process based on accident report analysis, expert evaluation and the development of structured coding guidelines. The reliability of the coding procedure was assessed using Fleiss’s kappa coefficient to evaluate inter-rater agreement. The proposed framework extends existing HFACS adaptations by incorporating cargo operation-specific organisational, operational and environmental factors. A total of 27 accident investigation reports related to tanker cargo operations were analysed. From these reports, 333 causal factors were identified and classified using the HFACS-TCO framework. The results show that tanker cargo accidents rarely arise from a single cause and usually involve multiple interacting organisational, operational and human factors. Most factors were identified at the levels of Preconditions for Unsafe Acts, Organisational Influences and External Factors, indicating that many accident conditions are established before unsafe acts occur at the operational level. The analysis also shows that most accidents involve factors across several HFACS levels, indicating that tanker cargo incidents develop through interactions between different system levels. The proposed HFACS-TCO framework provides a structured, domain-specific approach to analysing tanker cargo accidents and supports a more systematic identification of organisational and human factors in tanker cargo-related operations.